1. Field of the Invention
This invention relates to method and apparatus for controlling reproduction speed of an optical disk, which detects the magnitude of a disk vibration after initial operation for an optical disk and adjusts the disk rotation speed based upon the vibration magnitude.
2. Description of the Related Art
As media for recording digital information, a Compact Disk (referred as xe2x80x9cCDxe2x80x9d hereinafter) or a Digital Versatile Disk (referred as xe2x80x9cDVDxe2x80x9d hereinafter) series are generally used. Such kinds of optical disks can record enormous quantity of information such as long-time moving pictures, and these recording media are continuously developed for higher speed to reproduce or record more data within shorter time.
However, this high-speed reproduction inevitably causes disk vibration because of weight or eccentricity of a disk. Such a disk vibration at high speed generates a loud noise and increase difficulties of servo controls such as a tracking control, a focussing control and a sled control, thus might cause an error in searching a recording or reproduction point. These situations, if occurred, make it impossible to record or reproduce data accurately.
Accordingly, for high-speed reproduction, a vibration magnitude should be detected first. To do this, the vibration magnitude may be detected based upon reproduced signals and then a rotation speed is decreased if the vibration magnitude exceeds a certain critical level. For these speed adjusting processes, a conventional art equips a shock sensor for detecting a magnitude of disk vibration while a disk is rotating. The shock sensor outputs electric energy proportional to a vibration magnitude. However, this method causes rise in cost due to the equipment of a shock sensor.
To reduce the cost, several apparatuses for reproducing an optical disk which can detect disk vibration magnitude based upon reproduced signals without an additional sensor during high-speed reproduction and adjust a rotation speed depending upon the detected vibration magnitude have been invented, and they have been filed with the Korean patent application No. 98-54951, 98-54952 and 99-176, respectively.
The method according to the Korea patent application No. 98-54951 detects both vibration and eccentricity of a disk using a tracking error signal and controls a spindle motor. For this process, it detects disk vibration depending upon how many times a tracking error signal exceeds a predetermined standard slice level for a given time, samples and holds the peak and bottom level of the tracking error signal, computes the difference between peak and bottom, and checks whether there is an eccentricity by comparing the difference with a standard level. After then, it does not decrease a current rotation speed in case that there is an eccentricity even though the detected disk vibration exceeds the predetermined level.
The method according to the Korea patent application No. 98-54952 (also filed in the U.S. Patent and Trademark Office) detects an unbalance magnitude of an optical disk and controls a rotation speed according to the detected magnitude. This method computes the unbalance magnitude using the difference between A and B of a photo diode in which A and B are signals converted from a reflected main beam, and adjusts a driving voltage applied to a spindle motor depending upon the computed unbalance magnitude.
The method according to the Korea patent application No. 99-176 rotates an installed optical disk at a predetermined initial reproduction speed, measures how much the optical disk vibrates based upon levels of a high-frequency signal reproduced from the rotating optical disk, and controls the reproduction speed depending upon the measured disk vibration.
The above conventional methods detect a vibration of an optical disk based upon levels detected from an optical disk as explained above. However, they are not able to guarantee an accuracy in calculating vibration magnitude since the signal level to use in detecting disk vibrating magnitude is very sensitive, therefore, the reproduction cannot be performed under the optimal maximum speed since it is difficult to detect the vibration magnitude in precision even though the vibration magnitude exceeds a certain level.
It is an object of the present invention to provide apparatus and method for controlling reproduction speed of an optical disk, capable of detecting the magnitude of disk vibration caused by a high-speed rotation, and adjusting its reproduction speed based upon the detected vibration magnitude.
It is another object of the present invention to subdivide the magnitude of disk vibration based on respective rotation speeds and to adjust the reproduction speed of an optical disk depending upon the detected vibration magnitude and a current speed range.
The reproduction speed control apparatus according to this invention comprises a driving means for rotating an inserted optical disk; a counting means for counting a prescribed signal derived from a tracking error signal of the rotating optical disk; and a controlling means for controlling a reproduction speed of the optical disk based on the counted value.
The method according to this invention comprises the steps of: rotating an installed optical disk; detecting the quantity of a prescribed signal derived from a tracking error signal which are combined from signals reproduced from the optical disk when the rotation speed reaches to a predetermined speed; and deciding whether to increase the rotation speed above the predetermined speed based upon the detected quantity of the prescribed signal.
In the present invention, the driving means drives an inserted optical disk to rotate, and the counting means counts the prescribed signal derived from the tracking error signal of the optical disk being rotated by the driving means.
After that, the controlling means calculates the magnitude of disk vibration from the value counted by the counting means, and increases the rotation speed of the optical disk if the vibration magnitude is allowable at the current speed range.